The invention relates to the field of intravascular delivery systems, and more particularly to modular molds for forming balloon.
In percutaneous transluminal coronary angioplasty (PTCA) procedures, a guiding catheter is advanced until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. A guide wire, positioned within an inner lumen of an dilatation catheter, is first advanced out of the distal end of the guiding catheter into the patient""s coronary artery until the distal end of the guide wire crosses a lesion to be dilated. Then the dilatation catheter having an inflatable balloon on the distal portion thereof is advanced into the patient""s coronary anatomy, over the previously introduced guide wire, until the balloon of the dilatation catheter is properly positioned across the lesion. Once properly positioned, the dilatation balloon is inflated with liquid one or more times to a predetermined size at relatively high pressures (e.g. greater than 8 atmospheres) so that the stenosis is compressed against the arterial wall and the wall expanded to open up the passageway.
Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilatation but not overexpand the artery wall. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilatation catheter can be removed therefrom.
After angioplasty procedures, restenosis may form in the artery at the original stenotic site, necessitating either another angioplasty procedure, or some other method of repairing or strengthening the dilated area. To reduce the restenosis rate and to strengthen the dilated area, physicians frequently implant an intravascular prosthesis, generally called a stent, inside the artery at the site of the lesion. Stents may also be used to repair vessels having an intimal flap or dissection or to generally strengthen a weakened section of a vessel. Stents are usually delivered to a desired location within a coronary artery in a contracted condition on a balloon of a catheter which is similar in many respects to a balloon angioplasty catheter, and expanded to a larger diameter by expansion of the balloon. The balloon is deflated to remove the catheter and the stent left in place within the artery at the site of the dilated lesion.
In the design of catheter balloons, the balloon design must be tailored to provide optimal performance for a particular application. An important consideration in the design of the dilatation catheter assemblies is the ability of the balloon to either or both retain and deploy the stent which is mounted thereon.
As such, what has been needed are molds for forming balloons having differing geometries while maintaining efficient manufacturing processes. The present invention satisfies these and other needs.
The invention is directed to modular molds for forming an inflatable member, in particular, balloons for use with balloon catheters and stent delivery systems. The detachable molds of the present invention include detachable segments including a generally cylindrical intermediate segment having an intermediate longitudinal dimension and an intermediate interior chamber with an intermediate inner diameter, and proximal and distal segments longitudinally disposed at opposing ends of the intermediate segment and having corresponding interior chambers.
In one embodiment the proximal and distal chambers each has a base at a first end adjacent the intermediate chamber and a second end opposite the first end. The proximal and distal chamber bases each includes a ridge sufficiently raised with respect to its adjacent intermediate chamber. The mold has an inner diameter at the proximal and distal ridges sufficiently larger than the inner diameter of the mold at the intermediate segment.
In another embodiment, the proximal and distal chambers each has a base at a first end adjacent the intermediate chamber and a second end opposite the first end. The mold has an inner diameter at the proximal and distal bases sufficiently smaller than the inner diameter of the mold at the intermediate segment. In one embodiment, the mold proximal and distal chambers further include, respectively, proximal and distal steps having vertical segments and disposed between the intermediate chamber and the proximal and distal bases, respectively. Additionally, the mold proximal and distal chambers include proximal and distal shoulder chambers, respectively. The proximal and distal shoulder chambers taper in a direction away from the intermediate chamber and form proximal and distal shoulder chamber angles with the longitudinal axis of the mold, respectively.
In another embodiment, the proximal and distal chambers each has a base at a first end adjacent the intermediate chamber and a second end opposite the first end, and proximal and distal recesses disposed between the intermediate chamber and the proximal and distal bases, respectively. The mold, has an inner diameter at the proximal and distal bases sufficiently smaller than the inner diameter of the mold at the intermediate chamber. The mold has an inner diameter at the proximal and distal recesses sufficiently smaller than the inner diameter of the mold at the proximal and distal bases.
The molds of the present invention can further include detachable proximal and distal extension shafts configured to connect the proximal and distal segments at their respective proximal and distal ends to a blow-molding machine. The molds of the present invention are preferably made from metals, more preferably, stainless steel, for ease of fabrication, to achieve good surface quality and temperature and corrosion resiliency.
Angioplasty and stent delivery balloons are made of polymeric materials. In general, the polymeric material is extruded into tubular shapes or parisons. The extruded tube is then formed into the balloon shape using a blow molding process. Apparatus of the balloon blow molding process comprises a mold, a temperature source, a pressure source, and a tension source. In the balloon molding process, the extruded tubing is placed inside the mold and subsequently, the mold is heated with the temperature source. The tubing is stretched longitudinally using the tension source. The tubing is also expanded radially with the pressure source. The mold is made into multiple parts or inserts with opening lines or parting lines for ease of access. The final balloon shape is mostly controlled by the mold geometric design and the process parameters. The molds are generally made from materials that can be formed into desirable shapes and are geometrically stable at elevated temperatures. The segments may be fabricated using machining methods consistent with the choice of material and quality requirements.